1. Field of the Invention
This invention relates to a process for making phosphite esters and more particularly relates to a process for making phosphite ester by reacting triphenyl phosphite with an alcohol in the presence of a catalyst.
2. Description of the Related Art
Production of phosphite ester by reacting phosphites with alcohols in the presence of alkaline catalysts such as sodium methylate, sodium decylate, sodium phenolate or potassium cresylate are known, see Guttag U.S. Pat. No. 3326939, Guttag U.S. Pat. No. 3437720, Friedman et al U.S. Pat. No. 3047608, and Hechenbleikner U.S. Pat. No. 3205257, all of which are incorporated herein by reference.
These processes can however result in the production of catalyst related impurities. For example, reacting triphenyl phosphite (TPP) with various alcohols using sodium methylate catalyst results in phenol distillate containing several catalyst-related impurities such as methanol, anisole, and water. These impurities result in reduced purity of the recovered phenol and less-pure phosphite esters, and require purification of the recovered phenol before reuse in manufacture of triphenyl phosphite.
When sodium methylate is used as a catalyst in reactions of triphenyl phosphite with alcohols, the sodium methylate produces sodium phenate, the actual reaction catalyst, but it also causes the formation of undesirable by-products.
Sodium methylate reacts with phenol to form sodium phenate and methanol, with the sodium phenate remaining as the actual reaction catalyst. The methanol reacts with phenol to produce anisole and water.
Anisole is relatively stable but remains as an impurity in the phenol distillate and the phosphite. Water reacts with phosphites to produce acidic phosphite compounds, thereby increasing the acid number and giving a less pure product. The less-pure product results in decreased filtration rates, primarily due to diphosphites formed from the reaction of phosphite and water.
Consequently, there is a need to provide a process which results in higher purity phenol distillate and higher purity product.